* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.container {
    width: 1200px;
    margin: auto;
}

.col {
    width: 33.333333%;
    float: left;
    /*加一些装饰效果*/
    height: 100px;
    background: lightseagreen;
}

/*响应式代码的结构*/
@media (max-width: 600px) {
    .container{
        width: 100%;
    }
    .col{
        width: 100%;
    }
}


/*清除浮动*/
.container::after {
    content: "";
    display: table;
    clear: both;
}
